The present application claims priority under 35 U.S.C. xc2xa7119 of German Patent Application No. 199 40 429.1, filed on Aug. 26, 1999, the disclosure of which is expressly incorporated by reference herein in its entirety.
1. Field of the Invention
The present invention relates to a rubber blanket sleeve for a channel-free rubber blanket cylinder of an offset printing machine.
2. Discussion of Background Information
Rotary printing machines use open ended printing blankets which are clamped onto printing cylinders in such a way that an axially extending clamping point is produced on the cylinder circumference, which represents a dead zone for the printing process. Therefore rubber blanket cylinders with channel-free rubber blanket sleeves have already been proposed that do not require an axial clamping channel. DE 27 00 118 C2 discloses a rubber blanket sleeve which has a dimensionally stable support sleeve made of plastic or a metallic material, onto which are placed seamless cylindrical layers of elastic materials, preferably rubber. A rubber blanket sleeve that is completely free of gaps and seams is thus produced, which is slid axially over the rubber blanket cylinder and affixed. It is not necessary for a printing blanket to be clamped.
EP 0 452 184 B1 disclosed providing a rubber blanket sleeve with a base layer of celled rubber with a broad compression elasticity modulus range. A hard, fiber-reinforced elastomer layer is affixed to the outside of this rubber blanket sleeve. The outermost layer is the usual covering rubber layer for the printing process.
EP 0 514 344 B1 discloses a gap-free rubber blanket sleeve, which has a seamlessly affixed, celled, compressible elastomer layer on a cylindrical support sleeve. This celled, compressible layer is encompassed by a layer which cannot be stretched in the circumferential direction. The outermost layer is the elastomer printing layer, which is known per se. The non-stretchable layer acts as a kind of binding band for the celled, compressible layer. By increasing the shearing rigidity of the compressible layer, this binding band limits the deformation that occurs with the unwinding contact during printing. By the initial stress exerted, the circumferentially non-stretchable layer sets the shearing rigidity of the rubber blanket sleeve, while its disposition underneath the outer printing layer effectively prevents this outer layer from moving in the circumferential direction, i.e., from forming a bead or bulge.
The production of the rubber blanket sleeve is very expensive due to the mounting of the non-stretchable layer. The compressibility of the rubber blanket sleeve is influenced by the properties of the binding band. The inevitable tolerance with regard to the winding tension of the binding band can lead to an insufficient uniformity of the properties of the product. But a more uniform production of the rubber blanket sleeve must be achieved in order to improve printing quality.
The present invention provides a rubber blanket sleeve of the type described at the outset which permits a good printing quality at a lower cost while preventing the formation of a bead or a bulge during unwinding contact of the outer printing layer.
In particular, the rubber blanket sleeve of the instant invention includes an inner, dimensionally stable support sleeve as a supporting layer and a thin bonding agent layer affixed thereto. A microporous, closed pore-containing, compressible elastomer layer is provided having a compressibility of the elastomer layer falling within the range between about 7% and 15% with 100 N/cm2 of load. The rubber matrix of the compressible layer has a tensile stress of greater than about 2.2 N/mm2 and less than about 15 N/mm2 with 100% elongation. A thin layer of a bonding agent is applied to the elastomer layer, an outer covering rubber layer is provided as a printing layer, and of the layers are composed of seamless, cylindrical bodies and are affixed to one another.
The compressible elastomer layer usually contains gas-filled hollow spaces which produce the compressibility of the entire structure due to the compression of the enclosed gas. The number and size of the gas bubbles here are set so that the compressibility falls in the range between about 7% and 15% with 100 N/cm2 of load (tested according to DIN 16 621). At issue is the relative compressibility, which represents the average thickness reduction with regard to the actual thickness, indicated in %, in the loading cycle defined by the DIN norm 16 621. The rubber matrix of the compressible layer, i.e., the rubber mixture without taking into consideration the hollow spaces contained therein, has a tensile stress of at least about 2.2 N/mm2 and at most about 15 N/mm2 with 100% elongation (tested according to DIN 53 504).
Surprisingly, it was noted out that a sufficient shearing rigidity of the compressible layer is achieved even without a reinforcing binding band that extends over the microporous layer.
In an advantageous embodiment of the invention, the microporous elastomer layer contains reinforcing materials. These materials are incorporated into the compressible layer during its manufacture. The shearing rigidity of the microporous elastomer layer can be variously selected by the reinforcing materials contained in it.
In another advantageous embodiment of the invention, the reinforcing materials are mixed-in short fibers or embedded nonwoven mats. The short fibers are already mixed in during the production of the rubber mixture for the microporous layer. The short fibers increase the shearing rigidity of the compressible layer beyond the known measure associated with elastomers.
In another advantageous embodiment of the invention, the reinforcing materials are woven cloth layers of foils. The microporous layer is thereby reinforced and its shearing rigidity is thus increased.
In another advantageous embodiment of the invention, a woven cloth, a foil, or a knitted cloth is affixed between the support sleeve and the microporous layer. During manufacture, this cloth or foil layer can function as a receiving support for the microporous layer and, at the same time, with the interposition of a suitable bonding agent, can provide for a favorable bonding to the metallic support sleeve. Therefore, the costly separation of the microporous layer and receiving support before the actual coating of the support sleeve can be avoided.
The invention produces a rubber blanket sleeve which does not require an outer binding band around the compressible layer and nevertheless assures a sufficient shearing rigidity of the compressible layer. The shearing rigidity of the compressible layer is further increased by the additional embodiments of the invention. The material dampening is also increased at the same time, as a result of which the rubber blanket sleeve can favorably dampen vibrations of the rubber blanket cylinder supporting it in the printing machine.
The present invention is directed to a rubber blanket sleeve for a channel-free rubber blanket cylinder of an offset printing machine. The rubber blanket sleeve includes an inner, dimensionally stable support sleeve arranged as a supporting layer, and a microporous compressible elastomer layer having a compressibility within a range between about 7% and 15% with a load of 100 N/cm2. The elastomer layer includes a rubber matrix having a tensile stress of greater than about 2.2 N/mm2 and less than about 15 N/mm2 with 100% elongation. An outer covering rubber layer is arranged as a printing layer. All of the layers are composed of seamless, cylindrical bodies and are coupled to one another.
In accordance with a feature of the instant invention, a thin bonding agent layer can be affixed to the support sleeve, and a thin layer of a bonding agent can be applied to the microporous elastomer layer. The thin bonding agent layer affixed to the support sleeve may be structured and arranged to affix the support sleeve to the microporous elastomer layer, and the thin layer of bonding agent applied to the elastomer layer may be structured and arranged to affix the microporous elastomer layer to the outer covering rubber layer. The microporous elastomer layer includes closed pores.
In accordance with another feature of the invention, the microporous elastomer layer may contain reinforcing materials. The microporous elastomer layer may include short fibers which are mixed therein. Further, the microporous elastomer layer may include woven cloth layers or foils.
According to still another feature of the present invention, one of a woven cloth, a foil, and a knitted cloth can be affixed between the support sleeve and the microporous elastomer layer. Further, a thin bonding agent layer can be affixed to the support sleeve, a thin bonding agent layer can be applied to the one of the woven cloth, foil, and knitted cloth, and a thin layer of a bonding agent can be applied to the microporous elastomer layer. In this way, the thin bonding agent layer affixed to the support sleeve may be structured and arranged to affix the support sleeve to the one of the woven cloth, foil, and knitted cloth, the thin bonding agent layer affixed to the one of the woven cloth, foil, and knitted cloth may be structured and arranged to affix the one of the woven cloth, foil, and knitted cloth to the microporous elastomer layer, and the thin layer of bonding agent applied to the elastomer layer may be structured and arranged to affix the microporous elastomer layer to the outer covering rubber layer.
The present invention is directed to a rubber blanket sleeve for a channel-free rubber blanket cylinder of an offset printing machine. The rubber blanket sleeve includes an inner, dimensionally stable support sleeve arranged as a supporting layer, a thin bonding agent layer affixed to the support sleeve, and a microporous, closed pore, compressible elastomer layer having a compressibility within a range between about 7% and 15% with a load of 100 N/cm2. The elastomer layer includes a rubber matrix having a tensile stress of greater than about 2.2 N/mm2 and less than about 15 N/mm2 with 100% elongation. A thin layer of a bonding agent is applied to the microporous elastomer layer, and an outer layer covering rubber layer is arranged as a printing layer. All of the layers are composed of seamless, cylindrical bodies and are affixed to one another.
The present invention is directed to a process of producing a rubber blanket sleeve for a channel-free rubber blanket cylinder of an offset printing machine. The process includes arranging an inner, dimensionally stable support sleeve as a supporting layer, and positioning a microporous compressible elastomer layer having a compressibility within a range between about 7% and 15% with a load of 100 N/cm2 over the support sleeve. The elastomer layer includes a rubber matrix having a tensile stress of greater than about 2.2 N/mm2 and less than about 15 N/mm2 with 100% elongation. The process further includes arranging an outer covering rubber layer as a printing layer, such that all of the layers are composed of seamless, cylindrical bodies and are coupled to one another.
According to a feature of the present invention, the process can further include affixing a thin bonding agent layer to the support sleeve, and applying a thin layer of a bonding agent to the microporous elastomer layer. The process may also include affixing the support sleeve to the microporous elastomer layer with the thin bonding layer affixed to the support sleeve, and affixing the microporous elastomer layer to the outer covering rubber layer with the thin layer of bonding agent applied to the elastomer layer.
In accordance with another feature of the invention, the process can include forming the microporous elastomer layer to include reinforcing materials. The microporous elastomer layer can include short fibers which are mixed therein. Further, the microporous elastomer layer can include woven cloth layers or foils.
According to sill yet another feature of the present invention, the process can further include coupling one of a woven cloth, a foil, and a knitted cloth between the support sleeve and the microporous elastomer layer. The process can also include affixing a thin boding agent layer to the support sleeve, applying a thin bonding agent layer to the one of the woven cloth, foil, and knitted cloth, and applying a thin layer of a bonding agent to the microporous elastomer layer. Moreover, the process can include affixing the support sleeve to the one of the woven cloth, foil, and knitted cloth with the thin bonding layer affixed to the support sleeve, affixing the one of the woven cloth, foil, and knitted cloth to the microporous elastomer layer with the thin bonding agent layer affixed to the one of the woven cloth, foil, and knitted cloth, and affixing the microporous elastomer layer to the outer covering rubber layer with the thin layer of bonding agent applied to the elastomer layer.